Influence of Sintering Atmosphere on the Physical and Electrochemical of LiFePO4/C

Abstract

LiFePO4/C was synthesized from a gel precursor with ferric iron and an organic chelating agent as carbon source. Reductive atmosphere of N2 + H2 with H2 content of 0-20 vol % was used in the sintering process of LiFePO4/C composites. The microstructures of the obtained LiFePO4/C particles were characterized by X-ray diffraction, field emission scanning electron microscopy, element analysis and particle size analysis. The results showed that suitable reductive sintering atmosphere was needed to get pure LiFePO4/C phase, but too strong reducibility led to the formation of iron phosphides, most of which was Fe2P. The amount of Fe2P increased with the increase of H2 content in the sintering atmosphere. The rate capability of LiFePO4/C was improved when the sintering atmosphere became more reductive, while the discharge capacity of 0.1C decreased, which was probably due to the appearance of Fe2P phase.